Supercomputing in Plain English Overview: What the Heck is Supercomputing? - PowerPoint PPT Presentation

Supercomputing in Plain English Overview: What the Heck is Supercomputing?. Henry Neeman, Director OU Supercomputing Center for Education & Research University of Oklahoma Information Technology Tuesday January 25 2011. This is an experiment!.

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Supercomputing in Plain English Overview: What the Heck is Supercomputing?

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Size: Many problems that are interesting to scientists and engineers can’t fit on a PC – usually because they need more than a few GB of RAM, or more than a few 100 GB of disk.

Speed: Many problems that are interesting to scientists and engineers would take a very very long time to run on a PC: months or even years. But a problem that would take a month on a PC might take only a few hours on a supercomputer.

Oklahoma has been awarded an NSF EPSCoR RII Intra- campus and Inter-campus Cyber Connectivity (C2) grant (PI Neeman), a collaboration among OU, OneNet and several other academic and nonprofit institutions, which will:

upgrade the statewide ring from routed components to optical components, making it straightforward and affordable to provision dedicated “lambda” circuits within the state;

upgrade several institutions’ connections;

provide telepresence capability to institutions statewide;

provide networking professionals to speak to data networks courses about what it’s like to do networking for a living.

Control Unit: figures out what to do next – for example, whether to load data from memory, or to add two values together, or to store data into memory, or to decide which of two possible actions to perform (branching)

If Scott sits across the table from you, then he can work on his half of the puzzle and you can work on yours. Once in a while, you’ll both reach into the pile of pieces at the same time (you’ll contend for the same resource), which will cause a little bit of slowdown. And from time to time you’ll have to work together (communicate) at the interface between his half and yours. The speedup will be nearly 2-to-1: y’all might take 35 minutes instead of 30.

Now let’s put Paul and Charlie on the other two sides of the table. Each of you can work on a part of the puzzle, but there’ll be a lot more contention for the shared resource (the pile of puzzle pieces) and a lot more communication at the interfaces. So y’all will get noticeably less than a 4-to-1 speedup, but you’ll still have an improvement, maybe something like 3-to-1: the four of you can get it done in 20 minutes instead of an hour.

If we now put Dave and Tom and Horst and Brandon on the corners of the table, there’s going to be a whole lot of contention for the shared resource, and a lot of communication at the many interfaces. So the speedup y’all get will be much less than we’d like; you’ll be lucky to get 5-to-1.

So we can see that adding more and more workers onto a shared resource is eventually going to have a diminishing return.

Now let’s try something a little different. Let’s set up two tables, and let’s put you at one of them and Scott at the other. Let’s put half of the puzzle pieces on your table and the other half of the pieces on Scott’s. Now y’all can work completely independently, without any contention for a shared resource. BUT, the cost per communication is MUCH higher (you have to scootch your tables together), and you need the ability to split up (decompose) the puzzle pieces reasonably evenly, which may be tricky to do for some puzzles.

It’s a lot easier to add more processors in distributed parallelism. But, you always have to be aware of the need to decompose the problem and to communicate among the processors. Also, as you add more processors, it may be harder to load balance the amount of work that each processor gets.

Load balancing means ensuring that everyone completes their workload at roughly the same time.

For example, if the jigsaw puzzle is half grass and half sky, then you can do the grass and Scott can do the sky, and then y’all only have to communicate at the horizon – and the amount of work that each of you does on your own is roughly equal. So you’ll get pretty good speedup.

What HPC gives you that you won’t get elsewhere is the ability to do bigger, better, more exciting science. If your code can run faster, that means that you can tackle much bigger problems in the same amount of time that you used to need for smaller problems.

HPC is important not only for its own sake, but also because what happens in HPC today will be on your desktop in about 10 to 15 years: it puts you ahead of the curve.